In the prior art it has been known for a long time to expand plastic preforms within so-called blow stations, usually by means of applying pressurised air, into plastic containers. Conventionally, the plastic preforms are introduced into a blow mould, the blow mould is subsequently closed, and the plastic preforms are expanded into plastic containers by means of applying pressurised air. After this expansion process, the container thus produced has to be taken back out of the blow mould. To this end it is required that mould parts or mould carrier halves are folded apart in order to allow in this way the containers to be removed.
Usually, a plurality of such blow stations is arranged on a so-called blow wheel or another carrier, so that several containers can be produced essentially at the same time. In the prior art, a cam which is arranged to be stationary in the base frame of this blow mould, drives a control shaft. The rotary movement induced thereby is transferred onto hinge levers. These hinge levers are connected to cantilevers of the mould carrier halves, so that the tension and compression forces transferred by the hinge levers generate the opening and closing movements of the mould carrier halves.
Such a device for blow moulding is known from DE 42 12 583 A1. Here, the two cantilevers of the mould carrier halves are pivotably arranged about a common pivot axis, and on these cantilevers, two hinge levers are in turn pivotably mounted. An actuating element actuates these two hinge levers, and this actuating element moves exactly along a centre line of the mould carrier. In this way, the blow moulds may be opened and closed in a reliable manner. However, the solution known from DE 42 12 583 A1 requires relatively high torques because not only pivoting or rotary movements occur here, but the actuating element also has to be displaced relative to a lever, in order to ensure symmetry with regard to the centre line.
It may be desirable to reduce the required torque for opening and closing the blow mould or the mould parts. Further, it may be desirable to reduce the mechanical loads on guide curves which initiate the movements of the mould parts. It may also be desirable to reduce the spatial requirement of such systems as much as possible.